The debate between advocates of free-will, compatibilism, and determism is certainly on-going. Recently The Philosophy Forum had a meeting with Tim Harding of The Logical Place with his views on the subject (PDF attached of his presentation). Behind the walled garden of Facebook Alice Knight continued the discussion with contributions from Philosophy Forum regular Leslie Allan, Tim Harding, Stephen Lawrence, Trick Slattery, and others. Leslie Allan post a summary of his views, leading to the amusing possibility of a debate between "the logical place" and "the rational realm"!
A very brief description of the differences between the three positions is required. Free will implies the ability of subject to choose between different courses of action. Determinism argues that only one course of events is possible, which is inconsistent with the existence of such will. In contrast, compatibilists will often argue that freedom is a situation where a subject had freedom to act according to their own determined motivations, without arbitrary outside restrictions. It is the freedom to act according to one's will. Arthur Schopenhauer's classic definition was: "You can do what you will, but in any given moment of your life you can will only one definite thing and absolutely nothing other than that one thing" (On the Freedom of the Will, 1839), or expressed in another form "Man can indeed do what he wants, but he cannot will want what he wants" (Albert Einstein, Mein Glaubensbekenntnis, 1932)
This "soft determinism", the "free will determinist" point of view, is utter chicanery, engaging in a "quagmire of evasion" (William James The Dilemma of Determinism, Unitarian Review, September, 1884). It confuses social and political theory with ontology and treats them on the same level; political liberalism plus philosophical determinism apparently equals free will. Kant sneered at the compatibalist approach: "we call the motion of a clock a free motion, because it moves its hands itself" (Immanual Kant, Immanuel The Critique of Practical Reason, 1788).
Physicalists - whether of the determinist or compatibalist subspecies - tend to treat metaphysical free will advocates a little unfairly. Certainly there is some supposed historic justification for this. The argument goes that because humans have a soul, they also have free will in order to have moral responsibility - a very big deal in the monotheistic worldview. However even the scholastics were a little more sophisticated than that. The 'soul', in this context, is easily recognised as 'the mind' to a more secular audience. Purely physical objects are governed by deterministic laws of nature. Human beings are are able to engage in rationalisation, cognition, and voluntaristic action - "a rational nature always possesses free choice" (Anselm of Aosta, De Libertate Arbitrii, c1085). Kant expressed a similar point of view in arguing that the capacity of the human mind to consider how something ought to be, rather than what it is, was indicitive of the existence of a rational free will, independent of empirical considerations - it is not contra-causal Free Will, as is often pejoratively described, but non-causal.
Whilst one can be ambivalent of the difference between free will and determinism, and even ignorant of making assigning certainty one way or the other, the incompatabilist will argue that both cannot be true, at least not at the same time. Some - acknowledging quantum indeterminism - argue that free will or determinism are both incorrect, insofar the that universe is indeterminate, events are probablistic, and are choices are not subject to free will. It is perhaps fairer then, rather than assigning this position as as "deterministic", insofar that probabilities will generate the universe as we know it.
Two serious challenges can be expressed towards contemporary advocates of metaphysical libertarianism; from above and below, if one likes. On a sociological level, there is some fairly clear evidence of the overwhelming influence of environmental factors on one's wilful expressions, including the influences of language, socialisation, and especially pollution (e.g., exposure to lead leads to impuslive behaviour, resulting in crimes). On the neurological level, there is indication that supposedly conscious and wilful actions, are initiated unconsciously first and consciously afterward.
Even if free will is an illusion, for immediate practical purposes it still seems to exist. Perhaps we freely choose to be determinists, or we are determined to choose free will; thus are the beginnings of a viciously circular infinite regression. Physicalist advocates take quite a risk when the elaborate existing deterministic knowledge to presuppose absolute adherence. It is an extraordinary leap of faith, and one which really cannot be completely established, because we lack the ability to step outside spatial-temporal confines by which we have conscious apperception and wilful decision-making. Indeed, this inability makes the debate between free will, compatibilism, and determinism is a pseudo-problem; a spurious problem that cannot be properly answered with certainty - but rather the erroneous parts must be discarded: "The way to solve the problem you see in life, is to live in a way that will make what is problematic disappear" (Ludwig Wittgenstein, Culture and Value, 1937).